Metal-to-Ligand Electron Transfer in Diiminopyridine Complexes of Mn−Zn. A Theoretical Study
- 31 July 2001
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 40 (18) , 4649-4655
- https://doi.org/10.1021/ic001457c
Abstract
A series of complexes ML2x+ (M = Mn−Zn, L = 2,6-bis(iminomethyl)pyridine) was investigated by theoretical methods. Electron transfer from the metal “t2g” orbitals to the ligand π* orbitals is reflected in the elongation of ligand C−N bonds and shortening of the Cpy−Cimine bonds. Using zinc complexes as references, these deformations could be used to quantify the number of electrons transferred. Strong transfer is found in low-spin MnL2+ (ca. 2 e) and in high-spin MnL2+ and low-spin MnL22+, FeL22+, and CoL2+ (ca. 1 e each). Smaller transfer is found in CoL22+, and the transfer is insignificant in high-spin MnL22+, NiL22+, and CuL22+. Analysis of the unpaired electron density on the metal (using the Staroverov−Davidson method) shows that the contribution of a biradical description, in which ligand radical anions are antiferromagnetically coupled to the metal center, is significant in most cases. In the case of CoL2+ and high-spin MnL2+, where the metal−ligand bond is weakened, it amounts to over 50% of the total transfer.Keywords
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